Lecture 7

Question 1

Most important causes for evolutionary change in populations

Answer 1

genetic drift and natural selection

Question 2

genetic drift definition

Answer 2

random fluctuations in allele frequencys, no selective pressure so its a random non adaptive change

Question 3

Genetic drift occurs because natural populations are

Answer 3

finite in size

Question 4

Random fluctuations in allele frequencies can

Answer 4

result in non adaptive evolution

Question 5

natural selection results in

Answer 5

adaptive evolution

Question 6

in genetic drift

Answer 6

both conclusions of hardy weinberg equasions have been violated

Question 7

conclusions of hardy Weinberg violated in genetic drift are

Answer 7

allele frequencys changed from generation to generation and genotype frequency were not equal to expect frequency of 0.25 AA+0.5 Aa +0.25 aa=1

Question 8

Evolution occurs through

Answer 8

genetic drift

Question 9

For genetic drift the alleles included in any generation are

Answer 9

a sample of the alleles of the previous generation

Question 10

all samples are

Answer 10

subject to sampling error or random variation

Question 11

proportions of alleles are likely to differ by

Answer 11

change alone, from the proportions they are drawn from

Question 12

genetic drift is

Answer 12

analogous to the null hypothesis in statistics

Question 13

genetic drift can cause

Answer 13

speiciation, without natural selection

Question 14

way to portray genetic drift

Answer 14

a random walk, you start with p=0.5, each generation there’s a equal probability that p will move higher or lower, no stabilizing force so p will wanted to 1 or 0, is fixed 0 is lost

Question 15

in any given generation alleles are more likely to get lost or fixed in

Answer 15

smaller populations

Question 16

we use the loss of — as a measure of the rate of genetic drift within a population

Answer 16

heterozygosity, H=2p(1-p)

Question 17

As the frequency of one allele approches 1

Answer 17

the frequency of heterozygotes declines, rate of inbreeding increases, can lead to interbreeding depression

Question 18

the probability of an allele becoming fixed equals

Answer 18

the alleles frequency in the population

Question 19

the allele is more liekly to become fixed in

Answer 19

small populations

Question 20

genetic drift proceeds faster in

Answer 20

small populations

Question 21

if an allele has just arisen by mutation and is represented by only one among the 2N gene copies in the population its frequency is

Answer 21

pt=1/(2N)

Question 22

Census size

Answer 22

number of adults we count

Question 23

in actual populations the census size is

Answer 23

greater than the number that actually contributes alleles to the next generation

Question 24

in effective population size the

Answer 24

rate of genetic drift is greater than would be expected using a populations census size

Question 25

effective population size (Ne) definition

Answer 25

the number of individuals in an ideal population in which the rate of genetic drift would be the same as in the actual population

Question 26

bottleneck

Answer 26

A severe temporary reduction in population size, sometimes occurs when a new population is established by a small number of colonists

Question 27

founder effect

Answer 27

genetic drift in a small colonizing population, if population grows large fast it will not be greatly altered, if it remains small genetic drift will decrease genetic variation and alter allele frequency, new mutations may restore genetic variation

Question 28

consequences of population bottlenecks

Answer 28

fixation of deletreious alleles which reduces survival and reproduction, increasing the extinction risk, and interbreeding depression

Question 29

interbreeding increases

Answer 29

homozygosity and decreases heterozygosity

Question 30

many lethal alleles are

Answer 30

recessive and rare

Question 31

inbreeding increases

Answer 31

homozygosity in individuals that are more liekly to share the same recessive deleterious alleles

Question 32

inbreeding depression

Answer 32

is the reuslting decline in fitness and fecundity that occurs when closely related individuals reproduce

Question 33

inbreeding depression is well known in

Answer 33

small captive populations on endangered species, we have special breeding programs to minimize inbreeding

Question 34

inbreeding also increases risk of extinction of

Answer 34

small populations in nature

Question 35

Neutral theory of molecular evolution definition

Answer 35

the great majority of mutations that are fixed are effectively neutral with respect to fitness and are fixed by genetic drift

Question 36

most genetic variation at the molecular level is

Answer 36

selectively neutral and lacks adaptive significance

Question 37

small minority of mutations in DNA are

Answer 37

advantageous and are fixed by natural selection, many are disadvantoeous and are eliminated by natural selection

Question 38

The neutral theory futher holds that

Answer 38

evolutionary substitutions at the molecular level proceed at a constant rate, so the degree of sequence difference between species can serve as a molecular clock

Question 39

molecular clock

Answer 39

enables us to determine divergence times between species

Question 40

in order to assign concrete dates

Answer 40

the clock must be calibrated by using the fossil record